This invention relates to a detective security system, and particularly to a laser detective security system.
Conventionally, a supersonic security system is used for protecting any illegal intrusion. The supersonic security system comprises a supersonic receiver and some electronic eyes which issue supersonic waves to an alert area. When this area is illegally intruded or any object within this detective range is moved, the receiver will produce an inducted signal in response to the shock of frequency to sound alarms through horns or speakers of the system.
Alternatively, as shown in FIG. 1, a series of laser detective devices powered by an electric power source 5 and each having a laser generator or laser tube 1 and a sensor 4 are arranged along a passage or confined area 7. Said laser tube 1 will emit a laser ray 2 across the passage or area 7 to be received by the corresponding sensor 4. Whenever any one of the laser rays 2 is interrupted by illegal intruder 6, an inducted signal will be produced in response to the ray interruption to sound alarms through horns or speakers of the security system.
It is found disadvantageous that the protection web composed of a plurality of laser rays is not tight enough. An experienced intruder with evil intention may intrude himself into the passage or alert area without interrupting any of the laser rays. That means the security system will perform no function for protecting the alert area or passage.